Re: Delrin Molds

From: markschanze (mark-s@inav.net)
Date: Wed Mar 25 1998 - 05:52:13 EET


We in the industry use silicone to mold because it naturally self-releases.
 Machinable plastics such as polypropylene also have self-releasing
characteristics. Polypropylene is not easy to machine due to it's low melt
temperature. Delrin is easier to machine but certain grades still create
lots of "hair" or melt build up on the cutter. The easier the material is
to cut and the better the cutting finish the less natural release
characteristics the material will have. Polypropylene will have an
unlimited mold life. Delrin will have a limited mold life. Therefore the
release agent one uses will determine the life of the mold. Delrin will
not take most release agents well. Since you are trying to mold from a
material that will ultimately be dependant upon the release agent used,
maybe a material that handles release agents well should be considered,
like aluminum. Machining aluminum versus delrin and expecting to hold
tolerances is a no brainer. Finishing delrin is a bitch! Freekote 700
from Dextor Hysol is a great release agent for aluminum. Depending on the
tolerances required I would prefer silicone. At the most I would build a
hybrid mold of machined aluminum for high toleranced features and encompass
the fixtures in silicone. Obviously I could go on for a while so I will
stop. Questions?

Mark Schanze
Molding Technology Manager
CIVCO Medical Instruments
 319 656 4447
marks@civcomedical.com

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